v4.2.0

• Fix re-connection logic in sl_collect(), restoring the behavior of the last major version. The function will now reconnect on most connection errors with a few exceptions such as authentication failure, end of dial-up stream, and internal errors.
• Add new return status of SLAUTHFAIL for sl_collect() to indicate a fatal error. The caller can choose to reconnect if desired.
• Add sl_set_protocol() to allow caller specified protocol version.
• Many small fixes and improvements.
• Update Mbed-TLS to v3.6.5.